The control of translation plays a critical role in the pathogenesis of many viruses. The inhibition of host protein synthesis is important for suppression of the host antiviral response, while the selective translation of viral mRNAs is important for virus propagation in the host. Translational control by vesicular stomatitis virus (VSV), the prototype rhabdovirus, is one of the best-studied examples among the nonsegmented, negative-stranded RNA viruses. Previous experiments have made it clear that VSV uses novel mechanisms to control translation that are distinct from those of other well-studied RNA viruses, such as picornaviruses and influenza viruses. The goal of this project is to determine these mechanisms by which VSV inhibits host protein synthesis and promotes viral protein synthesis. Previous work has shown that the translation factor elF2alpha is inactivated in VSV-infected cells as a result of phosphorylation by protein kinase R. However, we have shown that the cap-binding elF4F complex is also inactivated in VSV-infected cells. Aim 1 is to determine how elF4F is inactivated, and the relative contribution of elF4F versus elF2alpha inactivation in the inhibition of host protein synthesis in VSV-infected cells. Aim 2 is to determine the viral components responsible for inducing the inhibition of host protein synthesis. These studies will use new recombinant viruses to map the genes of VSV mutants that are either more effective or less effective than wild-type VSV in the inhibition of host translation. Aim 3 is to determine the basis of resistance of viral mRNAs to the inhibition of translation. These experiments will use chimeric mRNAs containing viral or host 5' and 3' untranslated regions to test for the presence of cis-acting sequences that enhance translation of viral mRNAs. We will also test recombinant viruses that express these chimeric mRNAs to determine whether mRNA synthesis by the viral transcriptase confers the resistance to the inhibition of translation. Upon completion of these experiments, we will have important new information about how viruses suppress the antiviral response in the host, and how they promote expression of their own gene products. The results of these experiments will be novel, because the mechanisms used by VSV differ substantially from those of other well-studied prototype viruses. Finally, it is very likely that there are host mRNAs that use mechanisms similar to those of VSV mRNAs to enhance their translation under conditions such as stress. Thus we expect to gain new insight into regulation of cellular translation under other conditions where the activities of translation initiation factors are inhibited.